1. Field of the Invention
The invention pertains to the field of valve actuators. More particularly, the invention pertains to actuator for butterfly or similar valves.
2. Description of Related Art
Butterfly valves are quarter-turn type shut-off valves in which a flat disc is turned within a pipe to control fluid flow through the pipe. A shaft passes through the pipe and the disc to rotate the disc, typically through a range of 90° of rotation. Similar quarter turn valves such as ball valves and plug valves operate similarly, using balls and cylinders instead of discs to shut off fluid flow.
The prior art design of actuator for butterfly valves is shown in FIG. 1, in which 1 is the section of pipe forming the outside of the valve and 2 is the disc or butterfly.
In prior art designs, an actuator is typically made up of many parts which need to be assembled into the actuator.
The actuator gearbox 6 is typically mounted to the valve 1 by a bracket 5 which is secured by bolts 4 around a packing nut 3 which allows the shaft 7 to pass through the valve body 1 and disc 2. A worm assembly 9 bearing a quadrant worm gear 8 attaches to the top of the shaft 7, and a valve position indicator 11, usually in the form of a flag as shown, is attached to the top of the worm assembly 9. A handle shaft 12, bearing a worm 13, is inserted through the side of the gearbox 6 to actuate the worm gear 9, which in turn turns the shaft 7 and rotates the disc 2 to operate the valve. A separate handle or knob 15 is attached to the handle shaft 12 either by splines, threading or by tightening a setscrew. Once the parts are assembled, a gearbox cover 10 is fastened down to cover the gearbox 6.
A threaded hole 14 in a side of the gearbox 6 provides a mount for a position sensor (not shown), usually an electrical switch, which senses the position of the worm gear 8. The position sensor is conventional and does not form part of the invention.
Thus it can be seen that in the prior art design at least nine or ten parts must be manufactured and assembled for a single actuator assembly, not counting conventional fasteners, washers, seals, etc. as might be needed. The assembled actuator must then be assembled to the valve by the bracket and fasteners, as shown.